Tidligere gjesteforelesninger og seminarer - Side 44

John Webb, Professor at University New South Wales, Australia

By Mihaela Pavlicev from Cincinnati Children's Hospital Medical Center

Riccardo De Bin (Department of Mathematics, University of Oslo) will give a seminar in the lunch area, 8th floor Niels Henrik Abels hus at 14:15.

The classical s-cobordism theorem classifies completely h-cobordisms from a fixed manifold, but it does not tell us much about the relationship between the two ends. In the talk I will present some old and new results about this. I will also discuss how this relates to a seemingly different problem: what can we say abobut two compact manifolds M and N if we know that MxR and NxR are diffeomorphic? This is joint work with Slawomir Kwasik, Tulane, and Jean-Claude Hausmann, Geneva.

I will survey the connection between the space H(M) of h-cobordisms on a given manifold M, several categories of spaces containing M, Waldhausens algebraic K-theory A(M), and the algebraic K-theory of the suspension ring spectrum S[?M] of the loop space of M. The results extend the h-cobordism theorem of Smale and the s-cobordism theorem of Barden, Mazur and Stallings to a parametrized h-cobordism theorem, valid in a stable range established by Igusa, first discussed by Hatcher and finally proved and published by Waldhausen, Jahren and myself.

Sune Toft, Dark Cosmology Centre, Niels Bohr Institute

Elizabeth Gillaspy, p.t. Münster (Germany) will give a talk with title "Wavelets and spectral triples for higher-rank graphs"  

Erik Bølviken (University of Oslo) gives a lecture with the title: Where models meet reality - The Solvency II regulation of  European insurance

Kimmo Kainulainen, University of Jyvaskyla

The Oslo-Seminar in Mathematical Logic will take place at the same time and in the same location as in the previous terms.

Thursdays 10.15 - 12.00 in the meeting room of floor 9 in the computer science building.

The Barratt nerve BSd X of the Kan subdivision Sd X of a simplicial set X \in sSet is a triangulation. The Barratt nerve is defined as taking the poset of non-degenerate simplices, thinking of it as a small category and then finally taking the nerve.Waldhausen, Jahren and Rognes (Piecewise linear manifolds and categories of simple maps) named this construction 'the improvement functor' because of the homotopical properties and because its target is non-singular simplicial sets. A simplicial set is said to be 'non-singular' if its non-degenerate simplices are embedded. There is a least drastic way of making a simplicial set non-singular called 'desingularization', which is a functor D:sSet -> nsSet that is left adjoint to the inclusion. The functor DSd^{^2} is the left Quillen functor of a Quillen equivalence where the model structure on sSet is the standard one where the weak equivalences are those that induce weak homotopy equivalences and the fibrations are the Kan fibrations. I will talk about the main steps of the proof that the natural map DSd X -> BX is an isomorphism for regular X. This implies that DSd^{^2} is a triangulation and that the improvement functor is less ad hoc than it may seem. Furthermore, I will explain how the result provides evidence that any cofibrant non-singular simplicial set is the nerve of some poset.   

We will have a “mingle” meeting. There will be updates from Kristine and Luc on the running of the institute. But fear not, there will also be plenty of time for informal chat and eating of cake. All are welcome to the lobby on the first floor.

A conference celebrating the work of Ragni Piene on the occasion of her 70th birthday.

By Claudio Sillero from University of Oxford (NB: Note the time!)

Jochen Weller, Ludwig-Maximilians Universität, Munich

Johan Peter Uldall Fynbo, Professor DARK cosmology Centre, Niels Bohr Institute, University of Copenhagen

Triangulated categories of motives over schemes are sort of the "universal derived categories" among various derived categories obtained by various cohomology theories like l-adic cohomology. Ayoub constructed them using the A1-homotopy equivalences and étale topology. I will introduce the construction of triangulated categories of motives over fs log schemes. Fs log schemes are kinds of "schemes with toroidal boundary," and A1-homotopy equivalences and étale topology are not enough to obtain all homotopy equivalences between fs log schemes. I will explain what extra homotopy equivalences and topologies are neeeded. 

Daniel Roy (Department of Statistical Sciences, University of Toronto) will give a seminar in the lunch area, 8th floor Niels Henrik Abels hus at 14:15.

Ulrik Bo Rufus Enstad (Oslo) will give a talk with title: Connections between Gabor frames and Noncommutative Tori

Abstract: A Gabor frame is a special type of frame in the Hilbert space of square-integrable functions on the real line. Gabor frames provide robust, basis-like representations of functions, and have applications in a wide range of areas. They have a duality theory which is deeply linked to Rieffel’s work on imprimitivity bimodules over noncommutative tori. We explore several links between Gabor frames and noncommutative tori, and show how operator algebras can be used to give alternative proofs of theorems from time-frequency analysis.  This talk is based on my Master’s thesis written at NTNU, which reviews Franz Luef’s work on the connections between Gabor frames and modules over noncommutative tori, as well as some joint work with Franz Luef.